A hydrometer graduated for specific gravity (a urinoineter is suitable), also a 6-iu. by 1-in. tube with a graduation at 5in. and other marks, will be required in testing milk. Pour some milk into the tube and float the hydrometer in it; if the milk is pure the hydrometer will sink until the mark 1032 is just visible at the surface of the milk; watered milk will have a gravity below 1030, and, if very had, 1020 to 1025; skimmed milk has a gravity from 1033 to 1035. Remove the hydrometer, fill the tube to the 5-in. mark, and leave it till the morning; then read off the number of divisions occupied by the cream. The divisions may be one-tenths or one-twentieths of an inch; if the former, then each division equals 2 per cent, of cream; if the latter^then each division equals 1 percent, of cream. A good milk will yield 8 to 12 per cent, of cream or 3 to 4 per cent, of fat. The figures given above hold true for the majority of milks, but a little latitude must be allowed j for instance, if the percentage of cream is twelve, then the gravity may be below 1()30, and yet the milk may be genuine, because the fat is lighter than the other materials.

A full chemical analysis is really necessary for detecting slight adulteration.